Selective trigger pull mechanism



Dec. 27, 1960 E. B. PERRINE SELECTIVE TRIGGER PULL MECHANISM Filed Jan. 2'7, 1958 INVENTOR. [mmell 5. Herr/ 76 BY United States Patent SELECTIVE TRIGGER PULL MECHANISM Emmett B. Perrine, 620 S. 8th St., Minneapolis, Minn.

Filed Jan. 27, 1958, Ser. No. 711,349

4 Claims. (Cl. 42-69) This invention relates to a new and novel type of apparatus for trigger mechanisms of firearms. More particularly, this invention relates to apparatus for selectively varying the trigger pull pressure that is necessary to discharge a firearm.

The terminology trigger pull pressure as used in his specification designates the amount of force that has to be applied by the finger to the trigger of a firearm to ischarge said firearm when it is properly cocked.

In firearms that are used for hunting, it is desirable that more pressure has to be applied to a trigger to dis- "harge the firearms than when the same or a similar firefarm is used for target practice. When a person is carry- ?ing a firearm through a field there is more of'a chance 'ithat the firearms will be accidently discharged than when {the same rifle is being used for target practice. Thus, for

hunting, a high trigger pull pressure is desirable since this decreases the likelihood of accidental discharge. But

in target shooting there is less likelihood ofaccidental discharge and a greater need for accuracy. An increase in the trigger pull pressure necessary to discharge a firearm also increases the likelihood of the firearm being pulled out of the sighted position when the trigger is pulled to discharge said firearm, thus for target shooting, a low trigger pull pressure is desirable. Also when hunting it may be desirable to switch from a high to a low 2,965,993 Patented Dec. 27, 1960 wherein the trigger pull pressure may be easily varied from a pre-selected high value to a pre-selected low value.

Still a further object of my invention is to provide a mechanism for a firearm whereby the operator thereof may instantly change from one of a plurality of uniform trigger pull pressures necessary to discharge a firearm to another by a simple hand movement, said change not requiring visual checking to insure that the mechanism is properly adjusted.

A further object of this invention is to provide apparatus for trigger mechanisms of a firearm wherein the same firearm may be readily adapted to be used for hunting in the open field or for target-shooting and have the appropriate trigger pull for each type of event or to readily change from one trigger pull pressure to another in either type of event.

Still a further object of this invention is to provide apparatus wherein the trigger pull pressure necessary to discharge the firearm may be readily varied between two or more pre-selected values. At the same time, the apparatus is to be such that it may be easily replaced with similar parts so that the high value and the low value of trigger pull force may be changed to two or more different pre-selected values. The various elements making up the aforementioned apparatus are to be such that they are inexpensive to produce and readily installable in mos existing firearms.

Other and further objects are those inherentin the invention herein illustrated, described in the claims, an will be apparent as the description proceeds.

To the accomplishment of the foregoing and related ends, this invention then comprises features hereinafter trigger pull pressure. For example, having sighted a fastmoving target, a temporary low trigger pull pressure would be desirable to minimize the chance of pulling the firearm from a sighted position while discharging the firearm. In order that the same firearm may be readily used for both hunting and target shooting and have the appropriate trigger pull pressure for each type of event withoutrequiring any time consuming adjustments, this a selected trigger pull mechanism has been developed. In apparatus previously devised for varying the trigger ,5 pull pressure it has been necessary to make screw driver adjustments which necessitates carrying tools around; or else to use a complex mechanism for adjusting the trigger pull pressure. Where a screw driver adjustment has to be made, there is encountered the task of remembering if the firearm had previously been adjusted for a high or a low trigger pull pressure; and the direction of the adjustment that has to be made, along with the number of turns of the screw that is required to obtain the desired trigger pull pressure. Further, it has not been possible, by the use of a simple mechanism, to manually.

make the'desired adjustment of the trigger pull pressure and still be assured tthat the pressure necessary to discharge the firearm will be the same quantity as that when the firearm was previously set to be discharged with the application of a like amount of force.

One of the objects of this invention is to provide a manual means for selectively adjusting the trigger pull pressure necessary to discharge a firearm. The mechanism is to be such that it may be readily used with most of the firearms presently available on the market. An- Otherobject of this invention. is to-provide apparatus fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed. The invention is illustrated by reference to drawings in which the corresponding numerals refer to the same parts and in which:

Figure 1 is a fragmentary side elevational view of the receiver portion of a firearm having the selective trigger pull mechanism mounted thereon, said mechanism being shown in a high trigger pull position in solid line and in a low trigger pull position in dotted line.

Figure 2 is a fragmentary bottom view of the receiver portion of the rifle with a portion of the selective trigger pull mechanism and the trigger removed therefrom to illustrate the mounting of the cam-shaft and the aperture for an operative connection between the cam -shaft and a portion on the trigger.

Figure 3 is a sectional view taken along lines 3-3 of Figure 5 looking in the direction of the arrows to illustrate the recessed portions on the cam mechanism.

Figure 4 is an enlarged fragmentary view showing the selective trigger pull mechanism mounted on the offset portion of the trigger and also illustrating the movement of said mechanism between a high trigger pull pressure positioned in solid line and a low trigger pull pressure positioned in dotted line.

Figure 5 is a perspective view of the cam mechanism used in the selective trigger pull device, said view illustrating the recessed portions of the device.

Figure 6 is a sectional view similar to that shown in Figure 3 to illustrate a modified embodiment of my invention wherein the recessed portions are provided on the cam-shaft.

Referring now to the drawings, and particularly to Figures 1 and 2, there is shown a side elevational view of the receiver portion of a firearm with the selective trigger pull mechanism, generally designated as '10,"mounted therein and a partial bottom view of said receiver portion. The receiver, generally designated as 11, has a frame portion or block 12 formed at the lower portion thereof and integral therewith adjacent the stock (not shown). A conventional grooved portion 13 is formed in the bottom of the block opposite the bolt 18. A trigger sear 15 is pivotally mounted on a scar pivot 16. The scar pivot 16 extends through apertures formed in the side portions of said block. At one end of the sear 15 is a firing member engaging portion 17 which, when in a cocked position, prevents the spring driven firing member 18 from moving forward until the trigger 14 is pulled, said firing member being slidably mounted in the bolt 18. A sear spring 19 is mounted in the recess 40, said recess being formed in the block on the opposite side of the pivot 16 from the firing member engaging portion 17. The spring is mounted in the recess such that it abuts the projecting portion 15A of the sear so as to pivot the firing member engaging portion 17 towards said bolt. This resists the pivotal movement of the trigger sear so as to release the bolt, but is not stronger by itself to prevent the bolt from sliding forward.

A trigger engaging sear portion 42 is formed on the Sear 15 in a vertical plane lying between a plane parallel thereto passing through the pivot 16 and a third plane parallel to the first two passing through the firing member engaging portion 17. When the gun is cocked, the trigger engaging portion 42 rests in a notch 20 formed in one end of the trigger. When the aforementioned portion rests in the notch, the sear 15 is prevented from pivoting until such time as the trigger 14 is pulled. The pressure required to be exerted on the trigger to overcome the counterforce of the spring 19 and to disengage the sear portion 42 from the notch 20 of the trigger is herein labeled sear release force.

The opposite end of the trigger 14 from the notch 20 is pivotally mounted on a pin 22, said pin being mounted in the block 12 in a horizontal plane located below a plane passing through the pivot 16 and rearwardly of the vertical plane passing through the firing member engaging portion 17. Formed integral with the trigger 14 on the portion of the trigger adjacent the pin 22 and below the block 12 is an offset 23. The selective trigger pull mechanism, designated as 10, is in part mounted on said ofiset and in part mounted in the portion of the block rearwardly of the pin 22. Of course, it is to be understoodthat firearms having trigger mechanisms other than the one herein disclosed may be provided with the trigger pull mechanism of this invention by using a slightly different mounting so that said mechanism will operate in the same manner and perform the same functions as the mechanism described in this specification.

A bolt 24 is mounted in an aperture formed in the offset and is held in a' position by the nuts 26 that are threaded on said bolt on either side of said offset. As it may be noted, the bolt 24 extends outwardly from the offset: on both sides thereof;

A transverse cylindrical bore 36 is made in the block 12 rearwardly of the pin 22 and parallel thereto. This bore extends transverse to the main body of the block and extends through said block. A second cylindrical bore 31 is made in the angular portion 28 of the grooved section of the block such that it extends upwardly into the bore 36. The longitudinal axis of this bore is perpendicular to the axis of the transverse bore 36 and lies substantially on the same straight line which would be formed by an extension oflthe longitudinal axis of the aperture in the offset 23. 1 a p The cam-shaft, generally designated as 32, having a handle 33 is positioned in the first bore; The shaft has a deep recessed portion 34 that has a depth equal to approximately one-half of the diameter of the shaft. A second recessed portion35 which has a depth of approximately ten/on eethousandths of an inch is formed in the same shaftadjacent the first recessed portion. The res cessed portions are selectively positionable to face the bore 31 by rotating the handle. The solid line position of the handle illustrated in Figures 1 and 4 shows the mechanism adjusted in a high trigger pull pressure position whereas when the handle is located in the position shown by dotted lines in the same figures, the mechanism is adjusted to a low trigger pull pressure position.

A flat ended rivet, generally designated as 37, having a small flat cylindrical head 37a at one end and an elongated cylindrical portion 37b at the opposite end is protitled. The elongated cylindrical portion 37b is inserted into the bore 36, the elongated cylindrical portion being of such length that the central shoulder portion 370 of the rivet will contact the surface of the groove when the end of the elongated portion engages the flat surface of the first recess 34. The coil spring 19 is mounted over the end of the bolt 24 such that it exerts pressure against one of the nuts 26 and the aforementioned central shoulder portion 37c of the rivet. The pressure exerted between these two elements by the spring is called spring pressure.

When the handle is moved to the low pressure position the deep recess 34 is moved so that it faces the bore 31. The spring pressure exerted against the central portion; of the rivet will cause the rivet to move into the deep re-j; cess, this allowing the spring to stretch and thus lessen;

the amount of force that is exerted by said spring against-f the offset portion of the trigger. For example, when the:

spring is in its elongated position and exerts an effective spring pressure of 12 ounces against the ofiset. When the handle is moved to the high pressure position, the smallrecess 35 faces the bore 36 and thus the spring is compressed. In the compressed condition the spring exerts a spring pressure of 36 ounces.

Thus the total trigger pull pressure in the high pressure position is 20 ounces sear release pressure plus 36 ounces spring pressure making a total of 56 ounces. When the handle is moved to the low pressure position, it has a 20 ounce sear release pressure plus 12 ounces of spring pressure giving a total of 32 ounces trigger pull pressure. Thus it can be seen that the trigger pressure necessary to discharge a firearm can be readily changed by manipulating the handle to either a high or a low pressure position depending upon whether the firearm is to be used for hunting or for target practice.

If a greater difierence in trigger pull pressure between the high and low pressure positionsthan that herein disclosed is desired, it may be obtained by using a larger camshaft; for example, five/sixteenths of an inch in diameter and keeping the depth of the recesses the same as those on a five/thirty-secondths of an inch diameter shaft. Using the same parts illustrated, a higher trigger pull pressure may be obtained in both the high and the low positions by adjusting the top nut on bolt 24 so that the nut will move outwardly from the offset portion. This will compress the spring to give a higher value of trigger pull pressure in both the'high and the low positions.

If a higher high and a higher low trigger pull pressure is desired and at the same time a greater difference between the two pressures is desirable, this may be obtained by using the same structure previously set forth except that a spring having a higher spring constance than the original spring 19 or a spring having the same characteristics except that it is longer than the one described may be used in place of the spring described in the discussion of this invention. Once the new spring has been inserted, the mechanism may'be utilized to'vary the high and low trigger pull pressure in the same manner as set forth in preceding paragraph.

'An intermediate trigger pull pressure between a high and low pull pressure may be obtained using the camshaft 33 as shown in Figure 3 by forming a third recess 38 therein .as illustrated in Figure 6. The depth of the recess 38 as illustrated is less than the depth of recess 34 but greater than the recess 35. Thus it may be seen that a plurality of trigger pull pressure positions may be located on the same cam-shaft by properly selecting the dimensions of said shaft and the recess formed there- 111.

The various dimensions and the various spring pressures set forth in this application have merely been for purposes of illustration and are in no way to be construed as limitations as to the various components that may be used wherein similar principles of operation are involved. Further it is to be understood that the precise trigger structure illustrated and described in this specification is in no way meant to be considered a limitation on my invention since it is obvious that the same mechanism could be used with triggers having different structures or that for example the spring could be secured directly to the offset without destroying the function thereof.

As many widely apparent different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein.

What I claim is:

1. In a firearm having a frame, a firing member mounted on said frame for movement between a cooked position and a firearm discharge position, means normally urging said firing member to firearm discharge position, sear means for releasably holding said firing member in a cocked position, trigger means mounted on said frame for limited movement between a position retaining said sear means in position to hold said member in a firing position and permitting said sear means to release said firing member from the cocked position, means mounted on the frame for selectively varying the force required to move said trigger means from a position retaining said sear means in a position to hold said member in a firing position and a position permitting said sear means to release said member, said means for selectively varying the force including a shaft mounted on the frame for movement between a plurality of preselected positions, a handle mounted on the shaft to extend outwardly from the frame for turning the shaft by hand, to said pre-selected positions, and elongated means including a spring for exerting a varying pressure against said trigger means to resist the movement of said trigger means to a firearm discharge position, said elongated means having one end portion connected to said trigger means and an opposite end portion resiliently urged into abutting contact with the shaft surface, said shaft having a recess formed therein into which said opposite end portion moves in one of said pre-selected positions to permit the spring to expand, and out of which said opposite end portion moves in another preselected position to again compress the spring whereby the force required to move 6 said trigger means to a discharge position is selectively varied.

2. In a firearm having a frame, a trigger mounted on the frame for discharging said firearm, a shaft rotatably mounted on the frame for rotation between a plurality of pre-selected positions, said shaft having at least one recess portion in the peripheral surface thereof and means mounted on the frame in abutting contact with the shaft and connected to the trigger for selectively varying the trigger pull pressure required to discharge said firearm upon rotation of said shaft between said pre-selected position, said means mounted to abut against the recess portion in one of said pre-selected positions, said means including a spring mounted to generally extend in a direction transverse to the axis of rotation of said shaft.

3. The apparatus of claim 2 further characterized in that a handle is mounted on said shaft to extend outwardly beyond the frame, the trigger has an offset, and the spring means includes adjustment means secured to said offset for mounting one end of said spring to adjustably compress said spring and a rigid member seated in the opposite end of the spring to bear against the shaft surface.

4. In a firearm having a frame, a firing member normally urged to a firing position, sear means on the frame for releasably holding the fire member at a cocked posi tion, said sear means normally urged to a fire member release position, trigger means mounted on the frame for coacting with said sear means to releasably hold the sear means in position to prevent the firing member from moving to a firing position, and means for selectively varying the force required to release said firing means, said means for selectively varying the force to release said firing means including a cam shaft mounted on the frame for rotation between a plurality of pre-selected positions, and spring means extending transversely to said cam shaft and into abutting engagement with said cam shaft for exerting a selectively varying pressure resisting the movement of the trigger means as said shaft is moved between the pre-selected positions, said cam shaft having at least one recess formed therein into which said spring means extends in one of said pre-selected positions and out of which said spring means is moved as the shaft is rotated to another pre-selected position.

References (Zited in the file of this patent UNITED STATES PATENTS 2,069,887 Laudensack Feb. 9, 1937 2,225,583 Blizard Dec. 17, 1940 2,274,195 Garrison Feb. 24, 1942 2,474,456 Barnett June 28, 1949 2,533,283 Pierce Dec. 12, 1950 2,780,882 Temple Feb. 12, 1957 

